ARMOURED DEFENCES. 
337 
With regard to casemate shields in masonry works, Diagrams Nos. 
Ill and IV, represent one of these, 9 ft. high, which is suitable for a 
25-ton or 38-ton gun. 
A smaller kind, 8 ft. high, has been used for guns below the 25-ton gun. 
This type of shield consists broadly of the supporting structure, 
which we call the shield frame, and the armour. 
The first point is to secure the frame to the masonry, so that it 
cannot be driven back. This is done either by extending the base and 
top plates into the masonry, or by the use of massive dove-tail pieces, 
under the frame, provided with stops. The base plates are also bolted 
down to the masonry. 
These shield frames are made of f-in. plate, and 6-in. by 6-in. angle- 
irons, and weigh from 8J to 10 tons each when empty. They are filled 
with concrete when erected. 
The armour generally consists of three thicknesses of 5-in. armour 
with intervals of 5 ins., filled with brickwork or concrete between them, 
and round the opening of the port there are strong wrought-iron 
frames to keep this filling in place. Between the inner plate and the 
shield frame there is an inch interval, usually filled with wood. Each 
thickness of armour is bolted to the one next behind it, and the rear 
plate to the shield frame. No armour bolts show in the casemate. 
The weight of three thicknesses of 5-in. armour is about 25 tons, 
and the weight of one of the smaller of these shields complete is about 
56 tons. 
Some of these shields are protected by two thicknesses of 8-in. 
plate, and some by three; in one instance—namely, in the shields 
for 38-ton guns, at Garrison Point Battery, Sheerness—there are three 
thicknesses of 10-in. plates. 
There is a modification of this type of shield suited to open batteries 
to which over-head cover can be added at pleasure; and in more recent 
casemated works for 38-ton guns, as at Seaforth Battery, Liverpool, 
and St. Helen's Fort, off the Isle of Wight, there is another, perhaps 
the best arrangement of all, in which the armoured protection occupies 
a frontage of 20 ft. between the masonry piers. 
The shields at Hoo and Darnet Forts, on the Medway, are of a 
somewhat different pattern, and the two-tier shields in Garrison Point 
Battery, Sheerness, and Picldecombe Battery, Plymouth Sound, are of 
another kind, shown in Diagram VII. 
In these shields the ports are generally cut for a lateral training of 
60°, elevations up to about 10°, and depressions down to 4°, according 
to the circumstances of the works. 
The next kind of protection to be noticed is that given to heavy 
guns mounted on turntables. These occur in certain positions where 
an extended lateral fire of about 120° is required—as at 
Spithead defences, St. Helen’s Fort . two turntables for 18-ton guns. 
Gibraltar 
Malta 
C Prince Albert’s Bastn. 'N 
\ King’s Bastion . [ f 
I Wellington Front ... f 0U1 
(.Alexandra Battery ... ) 
n ...Sliema Battery ..two 
a 3 8-ton ii 
II li II II 
Casemate 
shields 
described. 
i 
Some shields 
have thicker 
armour. 
Open bat¬ 
tery shields. 
Seaforth and 
St. Helen’s 
shields. 
Hoo and 
Darnett 
shields. 
Two-tiered 
shields. 
Range of fire 
in shield 
ports 
generally. 
Casemates 
for heavy 
guns on 
turntables. 
